The major objective of the proposed research is to determine whether and to what extent exercise can offset or ameliorate the effects of psychological stress factors (stressful social environments or individual behavioral and psychophysioloigcal responses to such environments) on he diet-induced atherosclerosis of monkeys. A specific aim is to determine whether strenuous, regular exercise can retard atherosclerosis or influence the behavioral or clinical patholoigcal risk variables generally associated with atherosclerosis (i.e., social dominance, high heart rate reactivitiy, high plasma lipid concentrations). A further aim is to determine whether the effects of exercise on atherosclerosis andrelated behavioral and clinical patholoigcal risk variables are different among animals subjected to a psychosocial stressor in comparison to non-stressed controls. Data produced by this experiment should increase basic knowledge regarding the behavioral and physioloigcal effects of exercise; these data also could bear directly on the design and implementation of human exercise intervention trials. The proposed experiment involves 80 adult male cynomolgus macaques (Macaca fascicularis), all fed an atherogenic diet and all living in social groups of five animals each. Monkeys will be divided into four equally sized segments, made equivalent for plasma lipid, behavioral, and psychophysiological responses. These four segments will be utilized in the following 2 x 2 factorial design: a) group I to be exposedto the psychosocial stressor and be sedentary; b) group II to not be exposed to the psychosocial stressor and be sedentary; c) group III to be exposed to the psychosocial stressor and to be exercised; d) group IV to not be exposed to the psychosocial stressor and to be exercised. Comparison of atherosclerosis and related behavioral and clinical patholoigcal risk variables among groups will provide data on the relative efficacy of exercise interventions.